Solve "The Firebase CLI login request was rejected or an error occurred" when behind a proxy on macOS

Today when I tried to login to Firebase CLI I ran into an issue that stopped me from logging in. After approving the login request on Google's login page, the page kept loading something (a page served on localhost) and eventually it went to this page:

I searched on Google, and I came across this StackOverflow answer. Looks like there's a known bug that Firebase CLI can't work properly behind a proxy. I quickly realized I have environment variable ALL_PROXY, http_proxy and https_proxy set because I'm using a proxy.

The ultimate solution is to use a system-wide proxy, which in this case Proxifier is a very good choice, should you're using macOS. This kind of software makes all traffic go through a SOCKS5 proxy, so you won't have to manually set the env variable and therefore the problem gets solved.